The construction of chicken X mouse hybridoma cell lines secreting chicken MAbs to selected antigens is proposed. A primary advantage in the construction of these hybridomas is the genetic differences between chickens and mammals which increases the chance of producing antibodies against highly conserved regions of mammalian proteins such as peptide hormones and growth factors. Because of this genetic difference, chicken MAbs could potentially be prepared to epitopes that are either weakly or non-immunogenic in mice or rats. Interspecies hybridomas have been prepared by fusing immune lymphocytes from a number of mammalian species with mouse myeloma cells. These hybridomas are primarily useful for studies unique to that species. However, chicken MAbs technology could potentially become as important as current mouse and rat MAb technology. The antibodies could find commercial application as research reagents, therapeutics, and in diagnostic kits. The major objective of the Phase I application is to examine the feasibility and optimal conditions for the preparation of chicken X mouse hybridomas secreting chicken MAbs to a selected model antigen. The hybridomas will be monitored by stability, growth and immunoglobulin production. Since it has been demonstrated that interspecies hybridomas prepared with mouse myeloma cell lines are generally unstable, a secondary objective will include the examination of selective chicken X mouse heteromyelomas as fusion partners that will support stable hybridomas when fused with immune chicken lymphocytes.